By Kim Se-jeong Forty-one private security guards hired for the PyeongChang Winter Olympics are showing symptoms of a norovirus infection, the Korea Centers for Disease Control and Prevention (KCDC) said Tuesday.According to the KCDC, they have been vomiting and suffering from diarrhea since Saturday. Among them, 21 cases were confirmed Tuesday night. "We suspect a norovirus is to blame for other patients with similar symptoms," a KCDC official said Tuesday. "But the ongoing survey will have the final say."The KCDC inspection team began an epidemiological survey Monday on all 1,025 security officers hired for the event. All were staying in the same building 15 kilometers north of PyeongChang, eating the same food and drinking the same water. The KCDC said they separated the 41 from the others not showing symptoms and suspended all from working while the survey is underway. The KCDC suspects food and water as the main culprits of the infection, and investigators are examining this. The water supply reportedly came from groundwater. The KCDC has banned the same food and water from being served any more. The KCDC also ordered the local government to dispatch water sanitary inspectors to other staff buildings using groundwater for the drinking supply. Buildings in the remote PyeongChang County aren't connected to the county's central water system.Nine hundred soldiers have been dispatched to temporarily carry out the work of the security officers until they are cleared to resume work. A norovirus infection is characterized by diarrhea, vomiting and stomach pain as well as fever and headaches. It is spread by the fecal-oral route. Preventive measures include hand washing and disinfection of contaminated places. The mass infection has increased security concerns ahead of the Winter Olympics whose opening ceremony is now only two days away. Tens of thousands of people, including athletes, assistant staff and local visitors, are expected to flock to the venues to watch the games between Feb. 9 and 25.The event is also drawing high-profile delegations, including Japanese Prime Minister Shinzo Abe and U.S. Vice President Mike Pence, who will take part in the game's opening ceremony.Lee Hee-beom, president of the PyeongChang Organizing Committee for the 2018 Olympics and Paralympic Winter Games, apologized for the infection and ensure that the situation was under control.